class entry:
    class rvalue:
        def __init__(self, v): self._v = v
        def get(self): return self._v
        def __repr__(self): return "|%r|" % self._v
            
    def incoming(self, event):
        temporal, node = event.data
        if temporal == "post":
            p2 = event.trail.operands.pop()
            p1 = event.trail.operands.pop()
            event.trail.operands.append(self.rvalue(p1.get() * p2.get()))
